In the field of nuclear medicine, there are a variety of radioisotope cameras to accomodate various types of diagnostic studies. In addition to a variety of camera types, there are a range of available detectors as well as stands on which the detectors are mounted and positioned.
As is well known, a scintillation camera produces an image on a cathode ray tube from the gamma rays emitted by the radionuclide introduced into the patient to be examined. The gamma ray or scintillation detector portion of the camera absorbs incoming gamma rays that penetrate the crystal of the detector. In the detector there is provided in front of the crystal a collimator which permits passage of only those gamma rays that travel essentially parallel to the axis of the holes of the collimator that pass through to the crystal. Since in different studies, different portions of a patient are required to be diagnosed, or alternatively different portions of the patient are needed to be consecutively studied, it is important that the detector can be quickly and easily positioned in the proper orientation at the desired location with a minimum of inconvenience to the patient and ease to the operator.
Regardless of the way this is accomplished, since the detector must be located to a specific point in space, there are three spatial coordinates to be concerned with, in addition to a specific tilting of the detector at that spatial location. To accomplish such three-dimensional location, typical prior art stands for scintillation detectors utilize a number of linear motions to move the detector to the desired position. Typically, nuclear camera stands comprise a vertical column to permit height adjustment of the detector. In addition, the vertical column is often provided on a mobile base to permit the equivalent of length and width adjustments. Sometimes the length or width adjustment is accomplished directly from the vertical beam by means of extendable arms which, together with the detector, can be moved up or down the vertical beam. In some progressive stands, the vertical beam is further provided with a pivotal yoke on which the camera may be tilted from a horizontal or other fixed orientation. All such stands, however, use to a greater or lesser degree, rectilinear coordinate geometry. Thus, it typically takes an operator three steps to move the detector to the desired location and orientation with respect to the patient. In addition, such movements typically require the use of a power mechanism for assistance.
The subject invention recognizes that the use of polar coordinates makes the positioning of the detector a simpler and more efficient task with less inconvenience to the patient. Given a sphere in free space surrounding a portion of the patient to be examined, the detector can be easily and quickly positioned to the desired location with a maximum of two steps which can be done in unison. In terms of polar coordinates, the inventive apparatus permits adjustment along the two angular displacements which uniquely define a point on a sphere of a given radius.